[dexter1]

The network-installs IRIX 6.5.22 tarballs found here are archives of the 6.5.22m installation directories as they appear on disk.

The disk images directory consists of tarballs of the entire disk images, so you either need to burn them on a cd or unpack them yourself.

The 6.5.22m installation media are called "overlay", except for the first disk: "Installation tools and overlay"
This is because IRIX installations consist of a base product "IRIX 6.5" and a separate quarterly update, or ovelays, to the base. These updates start at 6.5.1 and end with 6.5.30.

IRIX 6.5.22m is the last IRIX which support Indigo1 systems, and the last IRIX which supported R4000 processors.

So if you want to perform a net install, use the network-installs tarballs and unpack them on a Linux machine. Next set up that machine as the irix-install bootp server using either my docker image, DINA or irixboot.